Patent EA-004622-B1 (EA)
Title: Treatment of metal sulphide concentrates
Inventor: JONES RODNEY TREVOR
IPC: C21C5/52
Filed: 2000-02-25
Abstract: 1. A process for treating a metal sulphide concentrate comprising at least one metal selected from the group comprising metals of platinum group, nickel, cobalt and zinc which includes the steps of roasting and smelting the concentrate under reducing conditions in an open arc furnace, chacacterised in that the concentrate is dead-roasted, and in that the concentrate is smelted under reducing conditions, in an electrically stabilized open-arc furnace (either a DC arc furnace or an electrically stabilized single electrode open arc AC furnace) in the absence of green furnace matte, so that the metal or metals collect in an alloy or vapour. 2. A process according to claim 1 wherein the roasting step is implemented in a way which produces a steady stream of SO2-bearing gas. 3. A process according to claim 2 which includes the step of using the SO2 bearing gas as a feedstock in a sulphuric acid plant. 4. A process according to claim 3 wherein the SO2-bearing gas which is released in the roasting step is subjected to gas scrubbing and neutralization. 5. A process according to claim 2, 3 or 4 wherein the roasting step is performed in an enclosed vessel to provide a high-concentration of SO2 in the gas. 6. A process according to claim 5 wherein the said vessel is a fluidized bed reactor. 7. A process according to any one of claims 1 to 6 wherein the reducing conditions are produced by the use of coke. 8. A process according to any one of claims 1 to 7 wherein zinc produced in the roasting step is melted under reducing conditions to metal vapour and is fumed off in a gas stream for recovery by condensation. 9. A process according to any one of claims 1 to 8, used for the treatment of zinc sulphide, wherein the concentrate after the roasting step is agglomerated before being fed to the arc furnace. 10. A process according to any one of claims 1 to 9 wherein the metal sulphide concentrate is a PGM concentrate in the form of green furnace matte. 11. A process according to any one of claims 1 to 10 which includes the step of removing iron, in oxide form from the said alloy. 12. A process according to any one of claims 1 to 10 which includes the step of removing carbon, silicon or chromium from the said alloy. 13. A process according to claim 12 wherein the removal step is effected using a converter and which includes the step of atomizing alloy from the converter so that it is in a form which is suitable for subsequent hydrometallurgical recovery of metal values. 14. A process according to claim 13 which includes the step of atomizing the alloy so that it is in a form which is suitable for subsequent hydrometallurgical recovery of metal values. 15. A process according to any one of claims 1 to 14 wherein the smelting step is a two-stage reduction smelting process. 16. A process according to claim 15 wherein, in a first stage, use is made of a furnace which is operated under slightly reducing conditions and, in a second stage, use is made of a stabilized open arc furnace which is operated under highly reducing conditions. 17. A process according to claim 16 wherein the second stage produces an ironbased alloy, and which includes the steps of atomizing the alloy and then subjecting the atomized alloy to hydrometallurgical treatment. 19. A process according to claim 16 or 17 wherein the first stage produces a copper/nickel alloy which is water atomized, granulated, or crushed and milled, and then subjected to hydrometallurgical treatment.